Polyorganosiloxane compositions which cure to elastomeric materials at room temperature are well known. Such compositions can be obtained by mixing polydiorganosiloxanes having reactive or hydrolyzable groups, such as silanol or alkoxy groups, with silane crosslinking agents, for example, alkoxysilanes, acetoxysilanes, oximosilanes, or aminosilanes, and catalysts as needed. Generally, the polydiorganosiloxanes may have 1 to 3 reactive groups per chain end. Compositions comprising these ingredients can then be cured by exposure to atmospheric moisture at room temperature.
The cure rate of a particular composition is dependent on a number of factors including the type of reactive or hydrolyzable group utilized. It is known that different hydrolyzable groups have different reactivities and even the same type of hydrolyzable group can have different reactivities. For example, in the presence of moisture, a silicon-bonded acetoxy group will hydrolyze more rapidly than a silicon-bonded alkoxy group. In addition if, for example, a silicon-bonded trialkoxy group is present on a polyorganosiloxane, it is believed that each silicon-bonded alkoxy group has a different reactivity, with the alkoxy group first reacted being "most reactive." Generally, once the first alkoxy group on a silicon atom reacts it takes a longer time for the second alkoxy group on the same silicon atom to react, and even longer for the third. Therefore, it would be desirable to prepare polyorganosiloxanes comprising at least one organofunctional group per molecule having more than one "most" reactive hydrolyzable group.
The objective of the present invention is to prepare a polyorganosiloxane comprising at least one organofunctional group per molecule having multiple hydrolyzable groups.